When operated at a constant current, the voltage (Vfor) of a forward-biased P/N diode exhibits a negative temperature coefficient of about −2 mV/° C. This property can be utilized to detect temperature. Unfortunately, the absolute value of Vfor varies according to diode composition and hence the process conditions under which the diode was fabricated. One approach to overcome such process-based variation in Vfor is to calibrate the current supplied across the P/N junction to match the variation in Vfor exhibited by a particular diode. However, such a calibration of individual current supplies is impractical for mass produced devices. Another approach is to detect a change in forward-biased diode voltage (ΔVfor) for two different applied currents, 1X and NX, where NX is a known multiple of 1X. Specifically:
                              T          =                                    q              ⁢                                                          ⁢                              ΔV                for                                                    η              ⁢                                                          ⁢              k              ⁢                                                          ⁢                              ln                ⁡                                  (                  N                  )                                                                    ,        where                            (        I        )            
T=absolute temperature (°K);
q=the charge on the carrier (electron charge);
ΔVfor=change in forward-biased voltage;
η=ideality factor of diode.
k=Boltzman's constant; and
N=ratio of the two applied currents.
The premise of this approach is the principle that any uncertainty in diode behavior introduced by process variation is eliminated (i.e., cancelled out) by detecting a voltage change for two different currents flowing across the same diode.
Conventional temperature sensors utilize a positive data pin and a negative data pin to sense the forward-biased diode voltage of each diode. Thus, the number of data pins required to monitor a diode is double the number of diodes being monitored. This use of data pins places a burden of the minimal architecture of modern integrated circuits, thus limiting the data pins available for other functions.